Abstract 2911: The CEA-targeted ISAC, BDC-2034, shows preclinical efficacy associated with innate immune activation, phagocytosis, and myeloid reprogramming

Introduction: Immune-stimulating antibody conjugates (ISACs) direct a TLR7/8 agonist into tumors through engagement of cell surface antigens to activate tumor-associated myeloid cells and initiate a broad innate and adaptive anti-tumor immune response. We are developing the ISAC BDC-2034 to target the tumor antigen, CEA (CEACAM5), which is expressed in many solid tumors. BDC-2034 comprises our proprietary antibody, CEA1, covalently conjugated to a potent TLR7/8 agonist via a non-cleavable linker. The strong pro-phagocytic capacity and slow internalization rate of CEA1 makes it an ideal antibody for the ISAC approach.

Methods: The ability of BDC-2034 to induce the secretion of pro-inflammatory cytokines was evaluated in vitro using co-cultures of tumor cells and primary immune cells (including monocytes and dendritic cells). Anti-tumor efficacy was demonstrated in vivo with xenograft and syngeneic mouse tumor models. In parallel studies, the mechanism of BDC-2034 action was assessed by quantifying intratumoral immune infiltration, cytokine levels, and transcript profile.

Results: In co-cultures of CEA-expressing tumor cells and immune cells, BDC-2034 induced the secretion of cytokines and chemokines that are essential for a broad anti-tumor immune response, including IL-12p70, CXCL10, and TNFα. These effects were accompanied by myeloid cell activation as demonstrated by elevation in costimulatory surface markers such as CD40. In vivo, BDC-2034 inhibited tumor growth in multiple xenograft and syngeneic mouse tumor models having CEA expression comparable to human cancers. Consistent with the proposed mechanism of action, BDC-2034 induced intratumoral immune cell infiltration, inflammatory cytokine secretion, and myeloid re-programming in a dose-dependent and CEA-dependent fashion. The constellation of BDC-2034 effects translated to durable therapeutic activity.

Conclusions: These preclinical findings demonstrate the potential of BDC-2034 to generate anti-tumor activity in CEA-expressing cancers through direct innate immune activation and the induction of adaptive anti-tumor immunity.

Citation Format: Lisa K. Blum, Cecelia I. Pearson, Laughing Bear Torrez Dulgeroff, Rishali Gadkari, Angela Luo, Andrew Luo, Jennifer E. Melrose, Jess L. Nolin, Hai Li, Arthur Lee, Matthew N. Zhou, Puneet Anand, Ganapathy Sarma, Karla A. Henning, Steven J. Chapin, Shelley E. Ackerman, Romas Kudirka, Yuyi Shen, Bruce Hug, Edith A. Perez, Marcin Kowanetz, Michael N. Alonso, Brian S. Safina, David Dornan, William G. Mallet. The CEA-targeted ISAC, BDC-2034, shows preclinical efficacy associated with innate immune activation, phagocytosis, and myeloid reprogramming [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2911.

Abstract 2883: Dectin-2 agonist antibodies reprogram tumor-associated macrophages to drive anti-tumor immunity

Tumor-associated macrophages (TAMs), an abundant immune cell population in most cancers, support tumor progression through their immunosuppressive effects. We discovered that TAMs express the pattern recognition receptor Dectin-2 (Clec4n/CLEC6A), an activating C-type lectin receptor (CLR) that binds to high-mannose glycans on fungi and other microbes and stimulates immune responses against infectious disease. Dectin-2 is selectively expressed by myeloid cells, and upon ligation, mediates enhanced phagocytosis, antigen processing and presentation, and proinflammatory cytokine production. Given these properties, we evaluated the therapeutic potential of targeting Dectin-2 to reprogram TAMs using natural ligands as well as our novel agonistic antibodies. We show that Dectin-2 agonists can convert TAMs into immunostimulatory cells in vitro and in vivo, and drive robust anti-tumor immunity.

Dectin-2 gene expression is minimal in normal human tissues but elevated across many tumor types, including breast, colon, lung, ovarian, and kidney cancers. We found that Dectin-2 is strongly expressed by macrophages differentiated in vitro and on primary TAMs from various solid tumors. Treatment of tumor-bearing mice with mannan, a natural Dectin-2 ligand derived from S. cerevisiae, mediated tumor regression in multiple syngeneic tumor models, with high rates of tumor clearance in the MB49 bladder cancer model. These effects were Dectin-2 dependent, as efficacy was not observed when a Dectin-2-blocking antibody was co-administered or in knockout mice lacking Dectin-2 signaling components. Depletion of either macrophages or CD8+ T cells impaired efficacy, suggesting that Dectin-2-stimulated TAMs augment anti-tumor CD8+ T cell responses. Based on these data, we developed novel Dectin-2-targeted agonist antibodies capable of activating both in vitro-generated and primary human TAMs to produce an array of proinflammatory cytokines and chemokines akin to tumor-destructive “M1” macrophages. Furthermore, systemically administered Dectin-2 agonist antibodies activated TAMs and mediated anti-tumor effects in immunodeficient mice engrafted with human CD34+ HSCs. The data presented demonstrate the therapeutic potential of Dectin-2 agonist antibodies as a novel pan-cancer approach for myeloid cell-directed tumor immunotherapy.

Citation Format: Justin A. Kenkel, Po Y. Ho, Karla A. Henning, Cindy L. Kreder, Jess L. Nolin, Sameera Kongara, Steven J. Chapin, Amreen Husain, Marcin Kowanetz, Edgar G. Engleman, Michael N. Alonso, David Dornan, Shelley E. Ackerman. Dectin-2 agonist antibodies reprogram tumor-associated macrophages to drive anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2883.

Abstract OT-03-02: Phase 1/2 study of a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), BDC-1001, as a single agent and in combination with an immune checkpoint inhibitor in patients with advanced HER2-expressing solid tumors

Background: To date, no immune-based therapies beyond anti-HER2 monoclonal antibodies are approved for treating patients (pts) with HER2-driven or -expressing cancers. However, pts still develop progressive disease, and new treatment options that could achieve durable antitumor efficacy are needed. Recent studies indicate that intratumoral delivery of immunostimulatory adjuvants such as toll-like receptor (TLR) 7/8 agonists can activate tumor resident antigen-presenting cells (APCs), driving uptake, processing, and presentation of tumor neoantigens to T cells that mediate antitumor immunity. To overcome limitations associated with intratumoral delivery while leveraging superior preclinical biology, BDC-1001, a novel, systemically delivered ISAC was developed. BDC-1001 consists of an investigational biosimilar of the humanized monoclonal antibody trastuzumab that is chemically conjugated to a TLR 7/8 agonist (payload) with an intervening non-cleavable linker. BDC-1001 activates human myeloid APCs while retaining antibody-mediated effector functions such as antibody-dependent cellular cytotoxicity/phagocytosis (ADCC/ADCP). Xenograft and syngeneic tumor resistant models indicate that trastuzumab ISACs elicit potent and durable immune-mediated antitumor efficacy including complete tumor regression in a TLR- and Fc receptor-dependent manner (Ackerman et al. Cancer Res. 2019:79 [13 Suppl]; Ackerman et al. J Immunother Cancer. 2019;7:283). Importantly, BDC-1001 did not induce interstitial lung disease, cytokine release syndrome, or thrombocytopenia in non-human primate studies. A four-part phase 1/2, first-in-human study has been initiated that evaluates BDC-1001 with or without (+/-) an immune checkpoint inhibitor targeting PD-1 in pts with HER2-expressing or HER2-amplified advanced/metastatic solid tumors.

Study Description: This phase 1/2 dose-escalation and dose-expansion study is enrolling up to 390 pts with advanced solid tumors that are HER2-expressing (IHC2+ or 3+ protein irrespective of gene amplification) or HER2-amplified (by in situ hybridization or next-generation sequencing) and ineligible for approved anti-HER2 treatments. The primary objectives of the dose-escalation phase are to define safety and tolerability and to determine the recommended phase 2 dose of BDC-1001 as monotherapy (Part 1) and in combination with an immune checkpoint inhibitor (Part 2). Primary endpoints of Parts 1 and 2 include incidence of 1) adverse events and severe adverse events graded according to NCI CTCAE v5.0; 2) dose-limiting toxicities within a 3+3 design; and 3) potential immune-related toxicities. BDC-1001 is administered IV over 60 min q3w at increasing doses. Once safety data are available for BDC-1001, initiation of the immune checkpoint inhibitor combination is planned. The dose-expansion phase 2 portion of the trial will evaluate preliminary antitumor activity of BDC-1001 alone (Part 3) and in combination with an immune checkpoint inhibitor (Part 4) using RECIST v1.1 and iRECIST. The primary endpoint of this dose-expansion phase is overall response rate, with secondary endpoints of duration of response, disease control rate, and progression-free survival. Exploratory objectives will evaluate pharmacokinetic parameters and pharmacodynamic biomarkers associated with drug exposure. These exploratory studies will help elucidate the mechanism of action and seek to identify biomarkers to improve selection of pts most likely to benefit from treatment with BDC-1001 +/- immune checkpoint inhibitor. This global study is currently recruiting pts. For further information, visit ClinicalTrials.gov (NCT04278144).

Citation Format: Ecaterina Ileana Dumbrava, Manish R. Sharma, Richard D. Carvajal, Daniel Catenacci, Leisha A. Emens, Shirish M. Gadgeel, Glenn J. Hanna, Dejan Juric, Yoon-Koo Kang, Jeeyun Lee, Keun-Wook Lee, Bob T. Li, Kathleen Moore, Mark D. Pegram, Paula R. Pohlmann, Drew Rasco, Alexander Spira, Antoinette R. Tan, Shelley E. Ackerman, Heidi LeBlanc, David Dornan, Marcin Kowanetz, Michael N. Alonso, Edith A. Perez. Phase 1/2 study of a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), BDC-1001, as a single agent and in combination with an immune checkpoint inhibitor in patients with advanced HER2-expressing solid tumors [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-03-02.

Immune-stimulating antibody conjugates elicit robust myeloid activation and durable antitumor immunity

Innate pattern recognition receptor agonists, including Toll-like receptors (TLRs), alter the tumor microenvironment and prime adaptive antitumor immunity. However, TLR agonists present toxicities associated with widespread immune activation after systemic administration. To design a TLR-based therapeutic suitable for systemic delivery and capable of safely eliciting tumor-targeted responses, we developed immune-stimulating antibody conjugates (ISACs) comprising a TLR7/8 dual agonist conjugated to tumor-targeting antibodies. Systemically administered human epidermal growth factor receptor 2 (HER2)-targeted ISACs were well tolerated and triggered a localized immune response in the tumor microenvironment that resulted in tumor clearance and immunological memory. Mechanistically, ISACs required tumor antigen recognition, Fcγ-receptor-dependent phagocytosis and TLR-mediated activation to drive tumor killing by myeloid cells and subsequent T-cell-mediated antitumor immunity. ISAC-mediated immunological memory was not limited to the HER2 ISAC target antigen since ISAC-treated mice were protected from rechallenge with the HER2- parental tumor. These results provide a strong rationale for the clinical development of ISACs.

Role of innate and adaptive immunity in obesity-associated metabolic disease

Chronic inflammation in adipose tissue, possibly related to adipose cell hypertrophy, hypoxia, and/or intestinal leakage of bacteria and their metabolic products, likely plays a critical role in the development of obesity-associated insulin resistance (IR). Cells of both the innate and adaptive immune system residing in adipose tissues, as well as in the intestine, participate in this process. Thus, M1 macrophages, IFN-γ-secreting Th1 cells, CD8+ T cells, and B cells promote IR, in part through secretion of proinflammatory cytokines. Conversely, eosinophils, Th2 T cells, type 2 innate lymphoid cells, and possibly Foxp3+ Tregs protect against IR through local control of inflammation.

Targeted Drug Delivery with an Integrin-Binding Knottin-Fc-MMAF Conjugate Produced by Cell-Free Protein Synthesis

Antibody-drug conjugates (ADC) have generated significant interest as targeted therapeutics for cancer treatment, demonstrating improved clinical efficacy and safety compared with systemic chemotherapy. To extend this concept to other tumor-targeting proteins, we conjugated the tubulin inhibitor monomethyl-auristatin-F (MMAF) to 2.5F-Fc, a fusion protein composed of a human Fc domain and a cystine knot (knottin) miniprotein engineered to bind with high affinity to tumor-associated integrin receptors. The broad expression of integrins (including αvβ3, αvβ5, and α5β1) on tumor cells and their vasculature makes 2.5F-Fc an attractive tumor-targeting protein for drug delivery. We show that 2.5F-Fc can be expressed by cell-free protein synthesis, during which a non-natural amino acid was introduced into the Fc domain and subsequently used for site-specific conjugation of MMAF through a noncleavable linker. The resulting knottin-Fc-drug conjugate (KFDC), termed 2.5F-Fc-MMAF, had approximately 2 drugs attached per KFDC. 2.5F-Fc-MMAF inhibited proliferation in human glioblastoma (U87MG), ovarian (A2780), and breast (MB-468) cancer cells to a greater extent than 2.5F-Fc or MMAF alone or added in combination. As a single agent, 2.5F-Fc-MMAF was effective at inducing regression and prolonged survival in U87MG tumor xenograft models when administered at 10 mg/kg two times per week. In comparison, tumors treated with 2.5F-Fc or MMAF were nonresponsive, and treatment with a nontargeted control, CTRL-Fc-MMAF, showed a modest but not significant therapeutic effect. These studies provide proof-of-concept for further development of KFDCs as alternatives to ADCs for tumor targeting and drug delivery applications. Mol Cancer Ther; 15(6); 1291-300. ©2016 AACR.

A Bioengineered Peptide that Localizes to and Illuminates Medulloblastoma: A New Tool with Potential for Fluorescence-Guided Surgical Resection

Tumors of the central nervous system are challenging to treat due to the limited effectiveness and associated toxicities of chemotherapy and radiation therapy. For tumors that can be removed surgically, extent of malignant tissue resection has been shown to correlate with disease progression, recurrence, and survival. Thus, improved technologies for real-time brain tumor imaging are critically needed as tools for guided surgical resection. We previously engineered a novel peptide that binds with high affinity and unique specificity to α_Vβ₃, α_Vβ₅, and α₅β₁ integrins, which are present on tumor cells, and the vasculature of many cancers, including brain tumors. In the current study, we conjugated this engineered peptide to a near infrared fluorescent dye (Alexa Fluor 680), and used the resulting molecular probe for non-invasive whole body imaging of patient-derived medulloblastoma xenograft tumors implanted in the cerebellum of mice. The engineered peptide exhibited robust targeting and illumination of intracranial medulloblastoma following both intravenous and intraperitoneal injection routes. In contrast, a variant of the engineered peptide containing a scrambled integrin-binding sequence did not localize to brain tumors, demonstrating that tumor-targeting is driven by specific integrin interactions. Ex vivo imaging was used to confirm the presence of tumor and molecular probe localization to the cerebellar region. These results warrant further clinical development of the engineered peptide as a tool for image-guided resection of central nervous system tumors.

The sociocultural dynamics of mass hysteria: a case study of social conflict in West Malaysia

This discussion of an episode of mass hysteria in a Malay college in West Malaysia examines stress and conflict in relation to the interpretive process within a specific social setting. Unlike previous studies, which conceptualize mass hysteria as a cathartic response to accumulated stress, the present study treats stress as a matter of definition in a specific sociocultural context rather than as an objective given from which predictions can be made. Objections are raised to the logic of explanations that attribute mass hysteria to environmental stress. What is of concern is how meanings are assigned to events that are experienced as stressful, how participants and observers explain these events, and the consequences that follow from their interpretations.